Do FIBROIDS cause complications ?M WORRIED,PLZ ANSWER-

HI ,I am in the early stages of pregnancy....5-6 weeks.i had an ultra sound done today to determine the age of the fetus.the doc said that she could see the sack but not the fetus and she could not hear the heart beat.
she said that it could be because the fetus may be behind a fibroid (a benign tumour). Do fibroids cause complications in future?
She asked me to get an ultra sound done after a week.
Has any body gone through this phase.Is there anything to worry about?was the ultrasound taken too early?any advice would be appreciated.thanx